Ignition system for internal combustion engines

ABSTRACT

The current-flow through the primary winding of an ignition coil of an ignition system for internal combustion engines is controlled by a pair of cascade-connected transistors each provided with negative feed-back means for stabilizing the current flow in the primary winding of the ignition coil. Additional control means include a thermally controlled resistor in the control circuit of one of said transistors arranged in heat-exchanging relation with the other of said pair of transistors so as to reduce the current flow through said pair of transistors and through said primary winding of said ignition coil in response to an undue increase of temperature of one of the transistors.

United States am 11 1 [111 3,902,471 Brungsberg Sept. 2, 1975 1 IGNiTioN SYSTEM FOR INTERNAL 3,605,713 9/1971 Lemasters 123/148 E COMBUSTION ENGINES 3,727,071 4/1973 Moran 123/148 E Inventor: Heinrich-Josef Brungslberg,

Ludenscheid, Germany Primary Examiner-Charles J. Myhre Assistant Examiner-Ronald 18. Cox Attorney, Agent, or F irm-Erwin Salzer ABSTRACT The current-flow through the primary winding of an ignition coil of an ignition system for internal combustion engines is controlled by a pair of cascadeconnected transistors each provided with negative feedback means for stabilizing the current flow in the primary winding of the ignition coil. Additional control means include'a thermally controlled resistor in the control circuit of one of said transistors arranged in heat-exchanging relation with the other of said pair of transistors so as to reduce the current flow through said pair of transistors and through said primary winding of said ignition coil in response to an undue increase of temperature of one of the transistors.

9 Claims, 2 Drawing Figures PAIEM'msEP-ws 31902 471 sum 1 OF 2 Q a: "i

IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention refers to ignition systems for internal combustion'engines including a d-c power supply, an interrupter. an ignition coil and at least one semiconductor switching device provided with a currentlimiting resistor. Interruption by the interrupter of the charging current flowing through the primary winding of the ignition coil releases the magnetic energy stored in the coil which then generates a high voltage in the secondary winding of the ignition coil. This high voltage is required to fire the spark plugs, thus igniting the compressed explosive mixture of air and gas within the cylinder, or cylinders, of the internal combustion engine.

Ignition systems for internal combustion engines generally include an ignition switch which, when its contacts are closed, establishes a circuit including the power supply or battery, the primary winding of the ignition coil and the interrupter for interrupting said circuit periodically. The d-c current supplied by the battery establishes a magnetic field in the ignition coils which collapses suddenly when the interrupter opens the circuit. The interrupter is operated by a cam which is mounted on the shaft of the distributor of the ignition system.

In conventional and now obsolescent ignition systems the interrupter interrupts the current which energizes the primary winding of the ignition coil. In more recent and more advanced ignition systems for internal combustion engines the current energizing the primary cir cuit of the ignition coil is switched on and switched off by means of a transistor. The interrupter having relatively movable contacts switches the base current, or control current. of the aforementioned transistor, which current is of a relatively small magnitude and does not tend to cause erosion of the contacts of the interrupter. The present invention refers to an ignition system of the aforementioned kind including a switching transistor for controlling the primary circuit of the ignition coil.

Prior art ignition systems of the aforementioned kind including a transistor are subject to the drawback, or limitation, that the power available for ignition depends largely upon the voltage of the power supply or battery. It is true that the magnitude of the charging current, or primary current, is largely determined by the constants of the primary circuit. However, in instances where the internal combustion engine is not operating and the ig nition circuit is closed, i.e. the ignition switch is closed and the contacts of the interrupter are in engagement, the primary current may be high and protracted and result in a far reaching discharge of the battery. As a result, such ignition systems for internal combustion engines are not capable of providing a substantially constant energy of ignition.

It is, therefore, one of the objects of the present invention to provide ignition systems for internal combustion engines tending to maintain constant the energy required for ignition, and to minimize losses occurring during periods of time when the internal combustion engine is not operating. Another object of the invention is to provide ignition systems. for internal combustion engines wherein the secondary voltage of the ignition coil is substantially constant over the entire range of number of revolutions per minute at which the internal combustion engine may be operated.

SUMMARY OF THE INVENTION lnition systems embodying; this invention include a transistor connected to be energized by a d-c power supply and an interrupter having relatively movable contacts arranged in the control circuit of said transistor for controlling the current. flow through said transistor. The transistor is provided with negative feed-back means for stabilizing the magnitude of said current flow through said transistor. Systems embodying this invention further include an ignition coil having a primary winding and a secondary winding and an additional transistor cascade connected to said transistor and con trolling the current flow through said primary winding of said ignition coil. The additional transistor is provided with additional negative feed-back means for stabilizing the magnitude of the current flowing through said additional transistor and energizing said primary winding of said ignition coil.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a wiring diagram of an ignition system for internal combustion engines embodying this invention;

FIG. 2 is a vertical section of a structure embodying this invention taken along IIII of FIG. 3; and

FIG. 3 is a topplan view of the structure shown in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 reference numeral 1 has been applied to indicate the interrupter of the ignition system. This interrupter controls the flow of current in a circuit which includes the positive pole of battery 2, the negative feedback resistor 3, the emitter 4a and the base 412 of transistor 4, thermally controlled resistor 5, resistor 6 and the mass of the internal combustion engine, or the neg-- ative pole of the battery 2, respectively. As a result of the flow of current in the aforementioned circuit a flow of current is established in a circuit which includes the positive pole of the battery 2, the negative feed-back resistor 3, the emitter 4a and the collector 4c of transistor 4, the base 7b and the emitter 7a of transistor 7, the negative feed-back resistor 8 and the negative pole of the battery 2. As a result of the aforementioned flow of current transistor 7 becomes conductive and now a current flows through a current path which includes the positive pole of battery2, the primary winding 9a of ignition coil 9., collector 7c and emitter 7a of transistor 7, negative feed-back resistor 8 and the negative pole of battery 2. The current flowing through winding 9a causes the storage of magnetic energy in ignition coil 9. When the contacts of interrupter 1 part, both thyristors 4 and 7 become non-conductive and, therefore, a high voltage discharge takes place in a circuit which includes the secondary winding 9b of ignition coil 9 and spark plug or spark plugs 21. In other words, the magnetic energy L/2 I which depends upon the maximum current flowing in the primary circuit of the induction coil 9 is transformed into electric energy in the secondary winding 9b of ignition coil 9 incident to opening of the contacts of the interrupter 1 and de-energization of transistors 4 and 7.

Reference characters 11 and 12 have been applied to indicate a pair of Zener diodes of which the former is operatively related to transistor 4 and the latter is operatively related to transistor 7. The object of Zener diodes ll and 12 is to stabilize the load current of both transistors 4 and 7. The base 4b of transistor 4 is conductively connected to the anode of Zener diode 11, and the cathode of the latter is connected to the positive pole of battery 2. The base 7b of transistor 7 is conductively connected to the cathode of Zener diode 12 and the anode of the latter is conductively connected to the negative pole of battery 2.

It is apparent from the above that the ignition system embodying this invention includes two currentstabilizing circuits, namely first Zener diode 11 and negative feed-back resistor 3 and transistor 4, and second Zener diode 12, negative feed-back resistor 8 and transistor 7. The peak values of the base currents and consequently the ignition energy in the secondary circuit of the ignition coil is substantially stabilized by means of the aforementioned current stabilizing circuits so as to substantially eliminate effects of variations of the voltage of the power supply or battery 2.

Reference numeral 13 has been applied to indicate a third Zener diode in the ignition system embodying this invention. The cathode of Zener diode 13 is conductively connected to a tap provided on the primary winding 9a of ignition coil 9 and the anode of Zener diode 13 is conductively connected to the negative pole of battery 2. Zener diode 13 limits the blocking voltage of transistor 7 and consequently the ignition voltage of the ignition system.

Considering a situation wherein, while the ignition system is operating, the secondary circuit of the ignition coil 9 is suddenly interrupted. This may result in excessive voltages in the secondary circuit of the ignition coil. These voltages appear also in the primary circuit of the ignition coil in a magnitude determined by the ratio of the two windings 9a, 9b. Excessive voltages induced in the primary winding 90 of coil 9 are blocking voltages as far as transistor 7 is concerned and may lead to a destruction of transistor 7. Zener diode l3 limits such voltages and also the maximum ignition voltage which may occur in the system.

Considering now a situation wherein the primary circuit of coil 9 is closed for an extended period of time because the contacts of interrupter l are closed and remain closed during an extended period of time during which the internal combustion motor is not operating. This tends to result in a continuous flow of current which drains battery 2 and results in losses which exceed by far the losses incident to normal operation of the ignition system (assuming that the contacts of the interrupter are closed during 50 percent of the time). Such excessive current flow causes overheating of transistor 7. Transistor 7 is thermally coupled, i.e. arranged in heat exchanging relation, with resistor 5. When the temperature of resistor is raised on account of excessive current flow through transistor 7, the resistance of the resistor 5 increases on account of its positive coefficient of temperature. The increase of the resistance of resistor 5 results in a decrease of the flow of current through transistor 4 which, in turn, reduces the base current flowing through transistor 7. Thus the losses in the circuitry are decreased in proportion to the square of the decrease of the current flowing through transistor 7. Thus the losses in the circuitry are decreased in proportion to the square of the decrease of the current and permissible current and temperature ceilings are maintained.

In FIG. 1 reference numeral 14 has been applied to indicate a fourth Zener diode shunted across a capacitor 15 which, in turn, is shunted across the two poles of the battery or power supply 2. This arrangement of parts provides protection against voltage spikes originating in the circuitry which is intended to charge the power supply or battery 2.

Coupling resistor 20 interconnects the base 71) and the emitter 7a of transistor 7.

All parts which are surrounded by a rectangular line 28 formed by dots and dashes are intended to be integrated into a self-contained structural unit shown in more detail in FIGS. 2 and 3. Reference numerals 17 and 18 have been applied in FIG. 1 to indicate the terminals of such a unit and reference character 19 has been applied in FIG. 1 to indicate a current-limiting resistor connected in series with interrupter l to form a base load.

The secondary circuit of ignition coil 9 includes resistor 16 and meter 24. That circuit further includes resistors 25, 26 and a spark gap 22 forming part of the distributor. Spark plug 21 is shunted by resistor 23 and by capacitor 27.

As shown in FIGS. 2 and 3 all the parts 3 to 20 shown in FIG. 1 are arranged in a common housing to which reference character 28 has been applied, ie the same reference character as has been applied to the dashand-dotted rectangle of FIG. 1. The arrangement of parts shown in FIGS. 2 and 3 dispenses with the separate housing means for the ignition coil 9 provided in conventional ignition systems for internal combustion engines. Reference numeral 28a has been applied to indicate a partition inside of housing 28 separating the same into a control circuitry compartment shown at the left of FIG. 2 and an ignition coil compartment shown at the right of FIG. 2. The latter is provided with an insulating bushing 29 for connecting secondary winding 9b of coil 9 to the distributor which, in turn, is connected to the spark plugs 21.

I claim as my invention:

1. In an ignition system for internal combustion engines energized by a d-c power source the combination of a. an ignition coil having a primary winding and a secondary winding;

b. a first transistor for controlling the current flow in said primary winding of said ignition coil, said primary winding of said ignition coil being arranged in the collector-emitter circuit of said first transistor in series with a first negative feedback resistor;

c. a first Zener diode interconnecting the base of said first transistor and one end of said first negative feedback resistor;

. a second transistor having a collector conductively connected to the base of said first transistor, the emitter of said second transistor being conductively connected to a d-c power supply by the intermediary of a second negative feedback resistor; and

ev a second Zener diode interconnecting the base of said second transistor and one end of said second negative feedback resistor.

2. An ignition system specified in claim 1 including a third Zener diode connected across a portion of said primary winding of said ignition coil to limit the magnitude of voltage spikes that may occur in said portion of said primary winding of said ignition coil.

3. An ignition system as specified in claim 2 wherein said third Zener diode is connected to a tap of said primary winding of said ignition coil positioned in such a way as to limit said voltage spikes to values compatible with the blocking voltage of said first transistor.

4. An ignition system as specified in claim 1 including a thermally controlled resistor arranged to reduce the base current in said second transistor upon increase of the ambient temperature of said resistor.

5. An ignition system as specified in claim 4 wherein said thermally controlled resistor is arranged in heatexchanging relation with said first transistor.

6. An ignition system as specified in claim 1 wherein said ignition coil, said first and said second transistor and said first and second Zener diode and additional electronic components are integrated into a structural unit.

7. An ignition system as specified in claim 6 including a housing being separated by an internal partition into two compartments, one of said compartments housing said first and second transistor, said first and second Zener diode and said additional electronic components, and the other'of said compartments housing said ignition coil.

8. An ignition system for internal combustion engines 6 energized by a d-c power supply including a. a transistor connected to be energized by said d-c power supply;

b. an interrupter having relatively movable contacts arranged in the control circuit of said transistor for controlling the current flow through said transistor;

c. negative feedback means for stabilizing the magnitude of said current flow through said transistor;

d. an ignition coil having a primary winding and a secondary winding;

e. an additional transistor energized by said d-c power supply, cascade connected to said transistor and controlling the current flow through said primary winding of said ignition coil; and

f. additional negative feedback means for stabilizing the magnitude of current flowing through said additional transistor and energizing said primary winding of said ignition coil.

9. An ignition system as specified in claim 8 including a resistor having a positive coefficient of temperature arranged in said control circuit of said transistor and in heat exchanging relation with said additional transistor to reduce the current flow through said primary winding of said ignition coil in response to an increase of the operating temperature of said additional transistor. 

1. In an ignition system for internal combustion engines energized by a d-c power source the combination of a. an ignition coil having a primary winding and a secondary winding; b. a first transistor for controlling the current flow in said primary winding of said ignition coil, said primary winding of said ignition coil being arranged in the collector-emitter circuit of said first transistor in series with a first negative feedback resistor; c. a first Zener diode interconnecting the base of said first transistor and one end of said first negative feedback resistor; d. a second transistor having a collector conductively connected to the base of said first transistor, the emitter of said second transistor being conductively connected to a d-c power supply by the intermediary of a second negative feedback resistor; and e. a second Zener diode interconnecting the base of said second transistor and one end of said second negative feedback resistor.
 2. An ignition system as specified in claim 1 including a third Zener diode connected across a portion of said primary winding of said ignition coil to limit the magnitude of voltage spikes that may occur in said portion of said primary winding of said ignition coil.
 3. An ignition system as specified in claim 2 wherein said third Zener diode is connected to a tap of said primary winding of said ignition coil positioned in such a way as to limit said voltage spikes to values compatible with the blocking voltage of said first transistor.
 4. An ignition system as specified in claim 1 including a thermally controlled resistor arranged to reduce the base current in said second transistor upon increase of the ambient temperature of said resistor.
 5. An ignition system as specified in claim 4 wherein said thermally controlled resistor is arranged in heat-exchanging relation with said first transistor.
 6. An ignition system as specified in claim 1 wherein said ignition coil, said first and said second transistor and said first and second Zener diode and additional electronic components are integrated into a structural unit.
 7. An ignition system as specified in claim 6 including a housing being separated by an internal partition into two compartments, one of said compartments housing said first and second transistor, sAid first and second Zener diode and said additional electronic components, and the other of said compartments housing said ignition coil.
 8. An ignition system for internal combustion engines energized by a d-c power supply including a. a transistor connected to be energized by said d-c power supply; b. an interrupter having relatively movable contacts arranged in the control circuit of said transistor for controlling the current flow through said transistor; c. negative feedback means for stabilizing the magnitude of said current flow through said transistor; d. an ignition coil having a primary winding and a secondary winding; e. an additional transistor energized by said d-c power supply, cascade connected to said transistor and controlling the current flow through said primary winding of said ignition coil; and f. additional negative feedback means for stabilizing the magnitude of current flowing through said additional transistor and energizing said primary winding of said ignition coil.
 9. An ignition system as specified in claim 8 including a resistor having a positive coefficient of temperature arranged in said control circuit of said transistor and in heat exchanging relation with said additional transistor to reduce the current flow through said primary winding of said ignition coil in response to an increase of the operating temperature of said additional transistor. 